Target selection for a small low-thrust mission to near-Earth asteroids

The preliminary mission design of spacecraft missions to asteroids often involves, in the early phases, the selection of candidate target asteroids. The final result of such an analysis is a list of asteroids, ranked with respect to the necessary propellant to be used, that the spacecraft could potentially reach. In this paper we investigate the sensitivity of the produced asteroids rank to the employed trajectory model in the specific case of a small low-thrust propelled spacecraft beginning its journey from the Sun-Earth $L_2$ Lagrangian point and heading to a rendezvous with some near-Earth asteroid. We consider five increasingly complex trajectory models: impulsive, Lambert, nuclear electric propulsion, nuclear electric propulsion including the Earth's gravity, solar electric propulsion including the Earth's gravity and we study the final correlation between the obtained target rankings. We find that the use of a low-thrust trajectory model is of great importance for target selection, since the use of chemical propulsion surrogates leads to favouring less attractive options 19\% of times, a percentage that drops to 8\% already using a simple nuclear electric propulsion model that neglects the Earth's gravity effects and thrust dependence on the solar distance. We also find that for the study case considered, a small interplanetary CubeSat named M-ARGO, the inclusion of the Earth's gravity in the considered dynamics does not affect the target selection significantly.